Ms Zaghari-Ratcliffe’s case has gained momentum in recent weeks after Boris Johnson, the foreign secretary, was heavily criticised for erroneously telling a parliamentary committee she had been “teaching people journalism” when she was arrested last year.

The 38-year-old charity worker is already serving a five-year prison sentence for allegedly planning the “soft toppling” of Iran’s clerical government while travelling to the country with her 22-month-old daughter.

The new charges could add 16 years to her prison term.

Zaghari-Ratcliffe’s BBC payslip. Click to enlarge

Last week, Iranian state television aired a seven-minute special report on Ms Zaghari-Ratcliffe which included close-ups of an April 2010 pay stub from her previous employer, the BBC World Service Trust.

It also included an email from June 2010 in which she wrote about the “ZigZag Academy,” a BBC World Service Trust project in which the trust trained “young aspiring journalists from Iran and Afghanistan through a secure online platform.”

Ms Zaghari-Ratcliffe left the BBC in 2011 and then joined the Thomson Reuters Foundation, the charitable arm of the news agency.

Both her husband, Richard Ratcliffe, and Thomson Reuters, have repeatedly stressed she was not training journalists or involved in any work regarding Iran while there.

Although Mr Johnson later corrected his remarks, the Iranian TV report made a point of highlighting them.

Mr Ratcliffe said the report and other Iranian comments about his wife seemed timed to exert as much pressure as possible on the British government.

He told the Associated Press the material appeared to be from his wife’s email, which investigators from the hard-line Revolutionary Guard immediately got access to after her arrest.

“It’s trying to justify the new charges,” Mr Ratcliffe said.

A spokesperson for BBC Media Action clarified Ms Zaghari-Ratcliffe never worked for BBC Persian.

They said she was employed as a projects assistant between February 2009 and October 2010 for the BBC World Service Trust charity.

“She further carried out some short-term contract work as an assistant for a project in Iraq for BBC World Service Trust,” the spokesperson added.

“Ms Zaghari-Ratcliffe was never a journalism trainer but undertook administrative duties such as travel bookings, typing, and filing.”

The report comes as Britain and Iran discuss the release of some £400m held by London, a payment Shah Mohammad Reza Pahlavi made for Chieftain tanks which were never delivered.

The shah abandoned the throne in 1979 and the Islamic Revolution soon installed the clerically overseen system which endures today.

Authorities in London and Tehran deny the payment has any link to Ms Zaghari-Ratcliffe.

However, a prisoner exchange in January 2016 which freed Washington Post journalist Jason Rezaian and three other Iranian-Americans also saw the United States make a $400m cash delivery to Iran the same day.

That money too involved undelivered military equipment from the Shah’s era, although some US politicians have criticized the delivery as a ransom payment.

Analysts and family members of dual nationals and others detained in Iran have suggested hard-liners in the Islamic Republic’s security agencies use prisoners as bargaining chips for money or influence.

A UN panel in September described “an emerging pattern involving the arbitrary deprivation of liberty of dual nationals” in Iran.